1. Field of the Invention
The present invention relates to a control device for parallel type hybrid vehicles in which the operation of a cylinder can be stopped. More specifically, the present invention relates to a control device for a hybrid vehicle which enables improvement in fuel consumption efficiency while maintaining salability when the vehicle is reaccelerated from a cylinder deactivated operation state.
2. Description of Related Art
Hybrid vehicles provided with a motor as an auxiliary driving source for running the vehicle in addition to an engine have been conventionally known. A parallel hybrid vehicle in which output from an engine is auxiliary assisted by a motor is a variation of the hybrid vehicles.
In the parallel hybrid vehicle, output from the engine is auxiliary assisted by the motor when the vehicle is accelerated, and various controls, such as charging of batteries using deceleration regeneration, are performed when the vehicle is decelerated so that the needs of the driver can be satisfied while maintaining remaining charge (electric energy) of the batteries. Also, the parallel hybrid vehicle, in terms of its structure, has a mechanism in which the engine and the motor are arranged in series. Accordingly, the parallel hybrid vehicle has advantages in that its structure can be simplified to decrease the weight thereof and to improve the degree of freedom in vehicle loading capacity.
The types of the parallel hybrid vehicle includes one in which a clutch is provided between the engine and the motor in order to eliminate the influence of engine friction (engine brake) during deceleration regeneration as disclosed in, for instance, the Japanese Unexamined Patent Application, First Publication No. 2000-97068, and one in which the engine, motor, and transmission are connected in series in order to maximally simplify its structure as disclosed in, for instance, the Japanese Unexamined Patent Application, First Publication No. 2000-125405.
However, the former in which the clutch is provided between the engine and the motor has disadvantages that its structure is complicated due to the presence of the clutch, which in turn deteriorates the loading capacity, and that its mechanical efficiency of power transmission during a running mode is decreased due to the used of the clutch. On the other hand, the latter in which the engine, motor, and transmission are connected in series has a regeneration amount decreased by the above-mentioned engine friction, and hence the amount of electric energy obtained by regeneration is reduced. Accordingly, it has problems in that the driving auxiliary (i.e., the amount of assist) etc. is restricted by the motor.
Also, in the former, a method for reducing engine friction during deceleration is available in which the amount of regeneration is increased by controlling a throttle valve to an open side during deceleration using an electronic control throttle mechanism in order to significantly decrease a pumping loss. However, there is a problem that a large amount of new gas directly flows into an exhaust system during deceleration to lower the temperature of catalyst or an A/F sensor, and exhaust gas control is adversely influenced.
With regard to the above, proposals have been made to solve the problem by using a cylinder deactivation technique. However, there is a problem in that smooth transition from a cylinder deactivated state to an all cylinder operation state is difficult.
Accordingly, an object of the present invention is to provide a control device for a hybrid vehicle which enables a smooth transition from the cylinder deactivated state to the all cylinder operation state using a cylinder deactivation technique so as to improve fuel consumption efficiency.
In order to achieve the above object, the present invention provides a control device for a hybrid vehicle provided with an engine (for instance, an engine E in an embodiment described later) including a plurality of cylinders and a motor (for instance, a motor M in the embodiment described later) as driving sources, in the vehicle a supply of fuel to the engine during a deceleration state of the vehicle is stopped and a regeneration control is performed by the motor in accordance with the state of deceleration, and the engine is a cylinder deactivatable engine capable of switching to an all cylinder operation state from a cylinder deactivated operation state in which at least one of the cylinders is deactivated, and vice versa, so that a cylinder deactivated operation of the engine is carried out in accordance with an operation state of the vehicle during deceleration, the control device comprising: an actual intake gas negative pressure detection unit (for instance, an inlet pipe negative pressure sensor SI in the embodiment described later) which detects an intake air negative pressure for the engine; an estimated intake gas negative pressure calculation unit (for instance, a step S201 shown in FIG. 5 in the embodiment described later) which estimates an intake air negative pressure based on a revolution number of the engine and an opening degree of a throttle, both the actual intake gas negative pressure detection unit and the estimated intake gas negative pressure calculation unit being used when the operation state of the engine is switched to the all cylinder operation state from the cylinder deactivated operation state, and a supply of fuel to the engine is about to be restarted by a fuel supply amount control unit (for instance, an FIECU 11 in the embodiment described later); and an engine control unit (for instance, also the FIECU 11 in the embodiment described later) which compares an actual intake gas negative pressure obtained by the actual intake gas negative pressure detection unit with an estimated intake gas negative pressure obtained by the estimated intake gas negative pressure calculation unit, the engine control unit prohibits a fuel supply to the engine until the actual intake gas negative pressure matches the estimated intake gas negative pressure, and carries out the fuel supply to the engine when the actual intake gas negative pressure matches the estimated intake gas negative pressure.
According to the above control device for a hybrid vehicle, it becomes possible, when returning to the all cylinder operation state to the cylinder deactivated operation state, to stop the fuel supply until the actual intake gas pressure matches the estimated intake gas negative pressure, and to restart the fuel supply quickly when the actual intake gas pressure matches the estimated intake gas negative pressure. Accordingly, as compared with the case where a fuel supply is restarted when the inlet pipe negative pressure is completely recovered, it becomes possible to shorten the time interval to the fuel supply and improve the salability during reacceleration after returning from the cylinder deactivated operation state.
In accordance with another aspect of the invention, in the control device for a hybrid vehicle, an initial value of fuel injection amount smaller than a normal fuel injection amount is set when the fuel supply is restarted, and an amount of the fuel supply is gradually increased until the fuel injection amount reaches the normal fuel injection amount.
According to the above control device for a hybrid vehicle, it becomes possible to suppress the generation of shock by gradually increasing the amount of fuel supply which is started when the actual intake gas negative pressure matches the estimated intake gas negative pressure. Accordingly, the salability during reacceleration can be improved.
In accordance with yet another aspect of the invention, in the control device for a hybrid vehicle, a predetermined amount of ignition retard is carried out when returned to the all cylinder operation state from the cylinder deactivated operation state, and an ignition timing is gradually returned to a normal ignition timing after restarting a fuel injection.
According to the above control device for a hybrid vehicle, it becomes possible to carry out an ignition retard of a predetermined amount immediately after returning to the all cylinder operation state from the cylinder deactivated operation state, and the delay of the ignition timing can be gradually returned to normal ignition timing. Accordingly, shock generated when returned to the all cylinder operation state can be decreased, and a smooth transition of the operation states can be performed.
In accordance with another aspect of the invention, in the control device for a hybrid vehicle, a driving force is assisted by the motor during a time period between fuel supply prohibition and a restart of fuel supply when returning to the all cylinder operation state from the cylinder deactivated operation state.
According to the above control device for a hybrid vehicle, it becomes possible to carry out acceleration using the motor during the time period between the fuel supply prohibition and a restart of the fuel supply when returning to the all cylinder operation state form the cylinder deactivated operation state. Accordingly, it becomes possible to maintain the acceleration performance during a time period in which no fuel is supplied, and hence, the salability can be improved.
The present invention also provides a control device for a hybrid vehicle provided with an engine including a plurality of cylinders and a motor as driving sources, in the vehicle a supply of fuel to the engine during a deceleration state of the vehicle is stopped and a regeneration control is performed by the motor in accordance with the state of deceleration, and the engine is a cylinder deactivatable engine capable of switching to an all cylinder operation state from a cylinder deactivated operation state in which at least one of the cylinders is deactivated, and vice versa, so that a cylinder deactivated operation of the engine is carried out in accordance with an operation state of the vehicle during deceleration, the control device comprising: an actual intake gas negative pressure detection unit which detects an intake air negative pressure for the engine; an estimated intake gas negative pressure calculation unit which estimates an intake air negative pressure based on a revolution number of the engine and an opening degree of a throttle, both the actual intake gas negative pressure detection unit and the estimated intake gas negative pressure calculation unit being used when the operation state of the engine is switched to the all cylinder operation state from the cylinder deactivated operation state, and a supply of fuel to the engine is about to be restarted by a fuel supply amount control unit; and an engine control unit which compares an actual intake gas negative pressure obtained by the actual intake gas negative pressure detection unit with an estimated intake gas negative pressure obtained by the estimated intake gas negative pressure calculation unit, the engine control unit determines a fuel supply amount based on the actual intake gas negative pressure when the actual intake gas negative pressure is larger than the estimated intake gas negative pressure, and determines the fuel supply amount based on the estimated intake gas negative pressure when the estimated intake gas negative pressure is larger than the actual intake gas negative pressure, and carries out the fuel supply.
According to the above control device for a hybrid vehicle, it becomes possible to supply a fuel, when returning to the all cylinder operation state from the cylinder deactivated state, based on one of the actual intake gas negative pressure and the estimated intake gas negative pressure, whichever is the greater, so that acceleration performance can be secured and the salability can be improved.
In accordance with another aspect of the invention, in the control device for a hybrid vehicle, a fuel injection amount based on the actual intake gas negative pressure is determined after returning to the all cylinder operation state from the cylinder deactivated operation state and a predetermined period of time has elapsed.
According to the above control device for a hybrid vehicle, a fuel injection amount based on the actual intake gas negative pressure is determined after a predetermined time period has elapsed even if a problem is caused, and hence reliability can be improved.
In accordance with another aspect of the invention, the control device for a hybrid vehicle further includes an ignition timing control unit (for instance, the FIECU in the embodiment described later) which controls an ignition timing, and the ignition timing control unit carries out an ignition timing control based on the actual intake gas negative pressure and the estimated intake gas negative pressure.
According to the above control device for a hybrid vehicle, it becomes possible to set a proper ignition timing corresponding to the fuel supply, and hence, acceleration performance when returned to the all cylinder operation state from the cylinder deactivated operation state can be secured.
The present invention also provides a control device for a hybrid vehicle provided with an engine including a plurality of cylinders and a motor as driving sources, in the vehicle a supply of fuel to the engine during a deceleration state of the vehicle is stopped and a regeneration control is performed by the motor in accordance with the state of deceleration, and the engine is a cylinder deactivatable engine capable of switching to an all cylinder operation state from a cylinder deactivated operation state in which at least one of the cylinders is deactivated, and vice versa, so that a cylinder deactivated operation of the engine is carried out in accordance with an operation state of the vehicle during deceleration, the control device comprising: a basic fuel injection amount calculation unit (for instance, the FIECU 11 in the embodiment described later) which calculates a basic fuel injection amount (for instance, a basic fuel injection amount TiM in the embodiment described later) based on an intake air negative pressure for the engine and a revolution number of the engine; and a fuel injection amount calculation unit (for instance, a step S401 shown in FIG. 12 in the FIECU 11 in the embodiment described later) which calculates a fuel injection amount (for instance, a fuel injection amount Ti in the embodiment described later) based on the revolution number of the engine and an opening degree of a throttle, both the basic fuel injection amount calculation unit and the fuel injection amount calculation unit being used when the operation state of the engine is switched to the all cylinder operation state from the cylinder deactivated operation state, and a supply of fuel to the engine is about to be restarted by a fuel supply amount control unit; and an engine control unit which compares a fuel injection amount calculated by the fuel injection amount calculation unit with a basic fuel injection amount calculated by the basic fuel injection amount calculation unit, and carries out a fuel supply based on a comparison result obtained.
According to the above control device for a hybrid vehicle, it becomes possible to compare the fuel injection amount with the basic fuel injection amount and a lower injection amount can be selected and set. Accordingly, acceleration performance can be secured while minimizing deterioration in the fuel consumption efficiency when returned to the all cylinder operation state from the cylinder deactivated operation state.